Field of the Invention
The inventions disclosed and taught herein relate generally to limit switches; and more specifically relate to adapters for proximity switches.
Description of the Related Art
Limit switches can be used in many operational environments to provide a changing electrical signal, such as by opening or closing a circuit, depending on the proximity of an object or target to the switch. Limit switches can be used for numerous different applications, which can include determining the presence, absence, passing, positioning, or end of travel of an object. In one common application, for example, a proximity switch, such as a magnetic proximity switch, can be used in conjunction with a valve to sense when the valve is in an open or closed position. Other types of limit switches include mechanical, lever arm type switches with an actuator linked to a set of electrical contacts; when the actuator comes in contact with an object, it can make or break an electrical connection.
A magnetic proximity switch can include a common electrical contact that is movable between two different contacts to complete either a first circuit or a second circuit. The common contact may include or be attached to a ferrous or magnetic sensing member that shifts in a first direction when a target, such as another magnet or ferrous structure, approaches within a certain distance, or sensing range, of the sensing member. The sensing member and/or the common contact may be biased to shift in a second direction when the target is disposed away from the sensing member beyond the sensing range. In this manner, the switch may make or break a circuit without physical contact between the sensing member and the target, whereas a lever arm switch may accomplish a similar result when the lever arm and an object move in and out of contact with one another.
Proximity switches can be used in relatively harsh operating environments, such as under water or in environments in which abrasives, such as dirt, metal shavings, and/or caustic chemicals, are present. Such environments can include sites for oil and gas extraction, chemical and petrochemical refineries, industrial plants such as steel mills, manufacturing and machining operations, and offshore or desert environments, among others. Proximity switches are also used in environments where fail-safe operation is of a top priority, such as nuclear power generation plants, and in environments in which equipment used must meet particular operating specifications, e.g., in order to prevent malfunctioning under extreme or other operating conditions. In nuclear applications, for example, some such specifications are intended to prevent malfunctioning of components under elevated seismic acceleration loading. In such applications, the center of gravity of a switch may be a relevant consideration in determining whether the switch is suitable for the application.
In some applications, it may be more desirable to use one type of limit switch instead of (or in some cases, collectively with) another type of limit switch. For instance, a magnetic proximity switch may be more desirable than a lever arm type switch in an application where it is desired or necessary to avoid contact between the switch and the target. In other instances, one may wish to replace one switch with another switch, such as when a switch has malfunctioned or surpassed its operating life. In these and other cases, a new switch may differ from an old switch, such as when switching from a contact switch to a contactless switch, from one switch manufacturer to another switch manufacturer, or from one switch arrangement to another switch arrangement.
When changing from one switch to another, such as from a lever arm switch to a magnetic proximity switch, etc., a problem can arise in that the bracketry or other mounting structure for the new switch may not match that of the old switch. Similarly, the mechanical attributes of the switches may differ, such as the masses, centers of gravity, or the like. This can call for design changes to existing equipment or other portions of a system, such as designs for new brackets, new targets, different electrical connections, or for other aspects of an application relating to the fit, form, or function of a switch at hand. In some cases, the time and expense of such changes can be significant, or even prohibitive. Thus, a need exists in the art for improved manners of replacing limit switches, including for replacing lever arm type mechanical switches with proximity sensors.
The embodiments disclosed and taught herein are directed to improved systems and methods for replacing limit switches.